Book of the Righteous is the classic pantheon product by Green Ronin. For me, and many others, this is the deity product that the Deities & Demigods should have been: a rich expose on the deities within, their lore, and details on their churches and followers.

This makes Book of the Righteous one of the most compelling sources for Pantheons for fantasy RPG settings.

This (PDF) version of the book splits off and updates the Holy Warrior's Handbook (also sold separately) to 3.5 mechanics. The Holy Warrior is, essentially, a Paladin whose abilities are largely replaced with "domains" to make it appropriate to deities other than Lawful Good deities, and further, reflecting specific aspects of the deities.

LIKED: The detailed, flavorful, and well written pantheon.

The Holy Warrior.

DISLIKED: Though the holy warrior was updated to 3.5, many of the remaining mechanics were never updated. Some character options need some attention to be playable.